FERMENTS, ENZYMES, TOXINS AND PTOMAINS 45 



gas as such is evolved: The fermentation best and longest 

 known to man is that through which sugar is converted 

 into alcohol, seen in the making of wine from grapes. In 

 so far as bacteria are concerned we are aware of a multipli- 

 city of reactions which are believed to be manifestations 

 of fermentation, though opinion on these points is far from 

 being in agreement. However, as ferments have never 

 been isolated in a pure state and as the real nature of their 

 activities cannot with the present means at our disposal, 

 be finally determined, there is as much justification for 

 regarding such reactions as excited by ferments as not. 

 We shall therefore assume that both the normal metabolism 

 of the bacterial cell and its peculiar power to excite specific 

 reactions in various substances are made possible through 

 the agency of ferments. In some cases such ferments are 

 firmly bound up as integral parts of the cell protoplasm. 

 To such cells with their peculiar ferments the term "organized 

 ferments" is often applied. The common yeast cell serves 

 as an example. In other cases the cells throw off in the 

 course of their living activities, as by-products so to speak, 

 bodies which, when completely separated from the cells by 

 which they were formed, are still capable of bringing about 

 fermentation reactions when mixed with appropriate sub- 

 stances, without themselves undergoing any demonstrable 

 change. These are denominated "unorganized ferments" 

 or "enzymes." 



In the case of the disease-producing bacteria we have an 

 analogous state of affairs. We find that the tissue changes 

 characterizing disease are due to poisons elaborated by the 

 living pathogens. These poisons are generically known as 

 toxins, and it is possible, though not certain, that in causing 

 disease their activities may be in some instances likened to 



